Quantization adjustment based on texture level

Abstract

A video encoder identifies a current smooth region of a current picture in a sequence and performs temporal analysis by determining whether a corresponding region in at least one previous and/or future picture is smooth. Based at least in part on the temporal analysis, the encoder adjusts quantization in the current smooth region. An encoder determines a differential quantization interval for a sequence, the interval comprising an interval number. The interval constrains the encoder to skip differential quantization for at least the interval number of predicted pictures after a predicted differentially quantized picture. An encoder analyzes texture in a current picture and sets a smoothness threshold. The encoder compares texture data with the smoothness threshold and adjusts differential quantization for at least part of the current picture based on a finding of at least one smooth region in the current picture according to the smoothness threshold.

We claim: 
     
       1. In a video encoder, a method comprising:
 determining a differential quantization interval for a video picture sequence, the interval comprising an interval number; 
 using the interval number when performing differential quantization for plural predicted differentially quantized pictures in the video picture sequence, wherein the interval number constrains the encoder to skip differential quantization for at least the interval number of predicted pictures after one of the plural predicted differentially quantized pictures, and only perform non-differential quantization on the predicted pictures for at least the interval number; 
 adaptively adjusting the interval number to change how many are skipped of the predicted pictures in which to have differential quantization; 
 wherein the adaptively adjusting is based on a type of content being encoded; and 
 outputting encoded data for the video picture sequence. 
 
     
     
       2. The method of  claim 1  wherein the differential quantization comprises:
 selecting one or more differential quantization step sizes for a first predicted picture of the plural predicted differentially quantized predicted pictures, the one or more differential quantization step sizes differing from a picture quantization step size for the first predicted picture; 
 changing the one or more differential quantization step size for a second predicted picture of the plural predicted differentially quantized predicted pictures, wherein the second predicted picture is outside the interval from the first predicted picture. 
 
     
     
       3. The method of  claim 1  wherein the plural predicted differentially quantized pictures comprise at least one P-picture. 
     
     
       4. The method of  claim 1  wherein the plural predicted differentially quantized pictures comprise at least one B-picture. 
     
     
       5. The method of  claim 1  wherein the differential quantization interval is a fixed interval. 
     
     
       6. The method of  claim 1  wherein the differential quantization interval is an adaptively adjustable interval. 
     
     
       7. One or more computer-readable non-volatile storage having stored thereon computer executable instructions to cause a computer to perform the method of  claim 1 . 
     
     
       8. One or more computer-readable non-volatile storage having stored thereon computer executable instructions to cause a computer to perform a method comprising:
 determining a differential quantization interval for a video picture sequence, the interval comprising an interval number; and 
 performing differential quantization for plural predicted differentially quantized pictures in the video picture sequence, but skipping differential quantization for at least the interval number after one of the plural predicted differentially quantized pictures; 
 performing quantization, other than differential quantization, on the interval number of the pictures in the video sequence for which differential quantization is skipped. 
 
     
     
       9. The one or more computer-readable non-volatile storage of  claim 8 , further including outputting encoded data for the video picture sequence. 
     
     
       10. The one or more computer-readable non-volatile storage of  claim 8 , wherein the differential quantization comprises:
 selecting one or more differential quantization step sizes for a first predicted picture of the plural predicted differentially quantized predicted pictures, the one or more differential quantization step sizes differing from a picture quantization step size for the first predicted picture; 
 changing the one or more differential quantization step size for a second predicted picture of the plural predicted differentially quantized predicted pictures, wherein the second predicted picture is outside the interval from the first predicted picture. 
 
     
     
       11. The one or more computer-readable non-volatile storage of  claim 8 , wherein the plural predicted differentially quantized pictures comprise at least one P-picture. 
     
     
       12. The one or more computer-readable non-volatile storage of  claim 8 , wherein the plural predicted differentially quantized pictures comprise at least one B-picture. 
     
     
       13. The one or more computer-readable non-volatile storage of  claim 8 , wherein the differential quantization interval is a fixed interval. 
     
     
       14. The one or more computer-readable non-volatile storage of  claim 8 , wherein the differential quantization interval is an adaptively adjustable interval based on a type of content being encoded.